The control of underarm wetness has been an issue of varying importance as far back as ancient Egypt and Rome, but it was not until the late 1880's that the first commercial antiperspirant products were introduced, using unbuffered zinc and aluminum compounds. Since then, many strides have been taken in this field and a wealth of antiperspirant products is now available in a wide range of delivery forms, including roll-ons, sticks and aerosol sprays.
The present inventors are primarily concerned with providing improved aerosol spray compositions. Delivery of antiperspirant actives by means of aerosol sprays may suffer from one or more of a number of disadvantages. These can include the necessity to shake the aerosol canister prior to use to achieve an adequate dispersion of active agents, “dustiness” or “powderiness” generated by particulates in the spray, visible residue on the skin and clothing, excessive cooling of the skin on application due to the rapid boiling off of propellant and, last but not least, skin irritation.
Prior investigators in this field have not been idle in recent years: U.S. Pat. No. 5,968,489 addresses the issue of skin irritation and identifies a particular solubiliser for the antiperspirant active that may assist in achieving that objective. WO 03/002082 aims to reduce or solve the problems of dustiness and visible residue by solubilising the active within an anhydrous emulsion.
A disadvantage of compositions taught in the prior art is their unsatisfactory adherence to skin following dispensing. This can result in a large proportion of the antiperspirant active flaking or wicking off leaving only a small amount to do the job it is intended to do. The slightly older teaching found in U.S. Pat. No. 4,806,338 does consider this matter and proposes the use of functionalised siloxanes to overcome it. Functionalised siloxanes proposed by U.S. Pat. No. 4,806,338 can be disadvantageous, however, in that they may react with the antiperspirant active agents, either via an acid-base reaction in the case of aminofunctional silicones, which are Lewis bases (the antiperspirant actives are Lewis acids), or via a chelation reaction (in the case of the carboxy-functional silicones), which reactions can reduce the efficacy of the active. In addition, functional silicones of the type taught by U.S. Pat. No. 4,806,338 may have reduced solubility in the aerosol propellants (and vice versa) which can give rise to inhomogeneity in the product with resultant inhomogeneity of deposition on the target site.
It would be beneficial to provide an antiperspirant aerosol composition that can overcome the above-described disadvantages of the prior art.